COMPRESS (JANUS DEFINE parameter) - Revision history

JAL: misc cleanup

2015-04-23T15:25:11Z

misc cleanup

← Older revision		Revision as of 15:25, 23 April 2015
Line 1:		Line 1:
	~~{{DISPLAYTITLE:COMPRESS}}~~
	<span class="pageSubtitle"> COMPRESS level — type of outgoing compression</span>		<span class="pageSubtitle"> COMPRESS level — type of outgoing compression</span>

Line 6:		Line 5:
	==Overview==		==Overview==
	Indicates the type of compression to be performed on outgoing <var class="product">[[Janus Web Server]]</var> data. Data compression reduces network bandwidth requirements for the compressed data but requires additional CPU resources to perform the compression. Janus provides deflate compression (RFC 1951), which is implemented on all modern web browsers and which works especially well for data that has frequently repeated, relatively long strings of bytes (for example, structured text data like HTML or XML).		Indicates the type of compression to be performed on outgoing <var class="product">[[Janus Web Server]]</var> data. Data compression reduces network bandwidth requirements for the compressed data but requires additional CPU resources to perform the compression. Janus provides deflate compression (RFC 1951), which is implemented on all modern web browsers and which works especially well for data that has frequently repeated, relatively long strings of bytes (for example, structured text data like HTML or XML).
	<p>		<p class="note">
	'''Note:''' No compression is ever performed on data with a mime-type that starts with '''image''' (for example '''image/gif''' or '''image/jpeg'''). Since most image formats are already compressed, trying to further compress them results in considerable CPU overhead and an ''increase'' in the size of the data sent (due to compression infrastructure overhead), but no real compression.</p>		'''Note:''' No compression is ever performed on data with a mime-type that starts with '''image''' (for example '''image/gif''' or '''image/jpeg'''). Since most image formats are already compressed, trying to further compress them results in considerable CPU overhead and an ''increase'' in the size of the data sent (due to compression infrastructure overhead), but no real compression.</p>

	==COMPRESS values==		==COMPRESS values==

	<table class="~~syntaxTable~~">		<table class="thJustBold">
	<tr><th>0</th>		<tr><th>0</th>
	<td>Perform no compression. This is the default.</td></tr>		<td>Perform no compression. This is the default.</td></tr>

	<tr><th>1</th>		<tr><th>1</th>
	<td>Perform deflate compression with fixed Huffman codes. This type of deflate compression uses a set of Huffman codes defined by the deflate specification. This can save space for some types of data, since the tables required for decoding are not sent with the data. The fixed code tables work well for text data. The fixed codes are rarely optimal, though, because they must include encodings for each possible character, even when those characters are not present in the data.</td></tr>		<td>Perform deflate compression with fixed Huffman codes.
			<p>
			This type of deflate compression uses a set of Huffman codes defined by the deflate specification. This can save space for some types of data, since the tables required for decoding are not sent with the data. The fixed code tables work well for text data. The fixed codes are rarely optimal, though, because they must include encodings for each possible character, even when those characters are not present in the data.</p></td></tr>

	<tr><th>2</th>		<tr><th>2</th>
	<td>Perform deflate compression with dynamic Huffman encoding. This type of deflate compression dynamically creates a set of Huffman codes that vary with the input data. This method creates an optimal set of codes for the data, but introduces a slight overhead because the decoding information must be sent with the data. This overhead is usually very small because the decoding tables themselves are also compressed with a special Huffman code. There is also a very slight CPU overhead in generating dynamic tables. Still, in most cases, dynamic codes yield better results than fixed codes. Since most text or character data consists of a relatively small number of characters, text data is usually a good candidate for, and gets fairly good compression with, dynamic Huffman encoding.		<td>Perform deflate compression with dynamic Huffman encoding.
	</td></tr>		<p>
			This type of deflate compression dynamically creates a set of Huffman codes that vary with the input data. This method creates an optimal set of codes for the data, but introduces a slight overhead because the decoding information must be sent with the data. This overhead is usually very small because the decoding tables themselves are also compressed with a special Huffman code. There is also a very slight CPU overhead in generating dynamic tables. Still, in most cases, dynamic codes yield better results than fixed codes. Since most text or character data consists of a relatively small number of characters, text data is usually a good candidate for, and gets fairly good compression with, dynamic Huffman encoding. </p></td></tr>
	</table>		</table>

Line 27:		Line 29:

	<ul>		<ul>
			<li>The <var>COMPRESS</var> setting on a port can be overridden on a URL basis with a <var>JANUS WEB ON</var> rule and on an application basis with <code>[[$Web_Set]]('COMPRESS')</code>. However, under <var class="product">Sirius Mods</var> Version 6.3, unless the <var>COMPRESS</var> parameter appears in the <var>JANUS DEFINE</var> command for a port, no compression will be performed no matter what the <var>JANUS WEB ON</var> rule or <var>$Web_Set</var> <var>COMPRESS</var> setting specifies.
			<p>
			Under <var class="product">Sirius Mods</var> Version 6.4 and later, '''no''' compression is performed unless the <var>[[NCMPBUF parameter\|NCMPBUF]]</var> system parameter is set to a non-zero value. If <var>NCMPBUF</var> is set to a non-zero value, the type of compression performed for a URL is determined by the <var>[[JANUS DEFINE]]</var> command, which can be overridden by a <var>JANUS WEB ON</var> rule, which can be overridden with <var>$Web_Set</var>. </p></li>

	<li>The <var>COMPRESS</var> setting on a port can be overridden on a URL basis with a JANUS WEB ON rule and on an application basis with [[$Web_Set]]('COMPRESS'). However, under <var class="product">Sirius Mods</var> Version 6.3, unless the <var>COMPRESS</var> parameter appears in the <var>JANUS DEFINE</var> command for a port, no compression will be performed no matter what the JANUS WEB ON rule or $Web_Set <var>COMPRESS</var> setting specifies.		<li>If you want no compression to be the default but want to apply compression selectively for some URLs or applications, you '''must''' explicitly specify <code>COMPRESS 0</code> in the <var>JANUS DEFINE</var> command, and, if <var class="product">Sirius Mods</var> Version 6.4 or later, you must specify a non-zero <var>NCMPBUF</var> value for User 0. </li>

	Under <var class="product">Sirius Mods</var> Version 6.4 and later, '''no''' compression is performed unless the <var>[[NCMPBUF parameter\|NCMPBUF]]</var> system parameter is set to a non-zero value. If NCMPBUF is set to a non-zero value, the type of compression performed for a URL is determined by the <var>[[JANUS DEFINE]]</var> command, which can be overridden by a JANUS WEB ON rule, which can be overridden with $Web_Set.

	<li>If you want no compression to be the default but want to apply compression selectively for some URLs or applications, you '''must''' explicitly specify <code>COMPRESS 0</code> in the JANUS DEFINE command, and, if <var class="product">Sirius Mods</var> Version 6.4 or later, you must specify a non-zero <var>NCMPBUF</var> value for User 0.

	<li>Under <var class="product">Sirius Mods</var> 6.3, a <var>JANUS DEFINE COMPRESS</var> setting allocates an extra compression buffer for each of the port's threads. This buffer is allocated at port START time, unless the <var>[[ALLOCC (JANUS DEFINE parameter)\|ALLOCC]]</var> parameter is specified on the port definition. If <var>ALLOCC</var> is specified, the compression buffer is allocated at the time a thread receives a connection. In either case, the compression buffer is large (almost 64K bytes), so if a port has 30 threads defined, compression requires an extra 30 * 64K, or 1,920K of virtual storage.		<li>Under <var class="product">Sirius Mods</var> 6.3, a <var>JANUS DEFINE COMPRESS</var> setting allocates an extra compression buffer for each of the port's threads. This buffer is allocated at port START time, unless the <var>[[ALLOCC (JANUS DEFINE parameter)\|ALLOCC]]</var> parameter is specified on the port definition. If <var>ALLOCC</var> is specified, the compression buffer is allocated at the time a thread receives a connection. In either case, the compression buffer is large (almost 64K bytes), so if a port has 30 threads defined, compression requires an extra 30 * 64K, or 1,920K of virtual storage.
			<p>
	Under <var class="product">Sirius Mods</var> 6.4 and later, a <var>JANUS DEFINE COMPRESS</var> setting allocates only as many extra buffers as the value of <var>NCMPBUF</var>, but these buffers are nearly five times as large as the 6.3 compression buffers.		Under <var class="product">Sirius Mods</var> 6.4 and later, a <var>JANUS DEFINE COMPRESS</var> setting allocates only as many extra buffers as the value of <var>NCMPBUF</var>, but these buffers are nearly five times as large as the 6.3 compression buffers. </p></li>

	<li>It is recommended that any site interested in using compression experiment with the <var>COMPRESS</var> parameter to determine compression efficiency and CPU overhead. <var class="product">Janus Web Server</var> issues message MSIR.0690 after compressing any data to indicate the success of the compression.		<li>It is recommended that any site interested in using compression experiment with the <var>COMPRESS</var> parameter to determine compression efficiency and CPU overhead. <var class="product">Janus Web Server</var> issues message MSIR.0690 after compressing any data to indicate the success of the compression.
	A typical message might look like this:		A typical message might look like this:

	<p class="code"> MSIR.0690: Janus Web content compressed by 65.2 -		<p class="code"> MSIR.0690: Janus Web content compressed by 65.2 percent from 8744 to 3048 bytes
	percent from 8744 to 3048 bytes		</p></li>
	</p>
			<li><var>COMPRESS</var> is valid only for <var>[[JANUS DEFINE#type\|WEBSERV]]</var> ports.</li>
	</ul>		</ul>

	~~<var>COMPRESS</var> is valid only for <var>[[JANUS DEFINE#type\|WEBSERV]]</var> ports.~~

	==See also==		==See also==

JALWiccan: Automatically generated page update

2013-04-16T21:52:27Z

Automatically generated page update

← Older revision		Revision as of 21:52, 16 April 2013
Line 1:		Line 1:
	{{DISPLAYTITLE:COMPRESS}}		{{DISPLAYTITLE:COMPRESS}}
	<span class="pageSubtitle"~~><section begin="desc" /~~> COMPRESS level — type of outgoing compression~~<section end="desc" />~~</span>		<span class="pageSubtitle"> COMPRESS level — type of outgoing compression</span>

	<var>COMPRESS</var> is a parameter on <var>[[JANUS DEFINE]]</var>, which defines and sets characteristics of a Janus port.		<var>COMPRESS</var> is a parameter on <var>[[JANUS DEFINE]]</var>, which defines and sets characteristics of a Janus port.

JAL2: /* Usage notes */

2012-06-22T21:04:00Z

Usage notes

← Older revision		Revision as of 21:04, 22 June 2012
Line 44:		Line 44:
	percent from 8744 to 3048 bytes		percent from 8744 to 3048 bytes
	</p>		</p>

	~~<li>The <var>COMPRESS</var> parameter is available in <var class="product">Sirius Mods</var> Version 6.3 and later.~~
	</ul>		</ul>

JAL2: /* Usage notes */

2012-06-22T21:03:07Z

Usage notes

← Older revision		Revision as of 21:03, 22 June 2012
Line 30:		Line 30:
	<li>The <var>COMPRESS</var> setting on a port can be overridden on a URL basis with a JANUS WEB ON rule and on an application basis with [[$Web_Set]]('COMPRESS'). However, under <var class="product">Sirius Mods</var> Version 6.3, unless the <var>COMPRESS</var> parameter appears in the <var>JANUS DEFINE</var> command for a port, no compression will be performed no matter what the JANUS WEB ON rule or $Web_Set <var>COMPRESS</var> setting specifies.		<li>The <var>COMPRESS</var> setting on a port can be overridden on a URL basis with a JANUS WEB ON rule and on an application basis with [[$Web_Set]]('COMPRESS'). However, under <var class="product">Sirius Mods</var> Version 6.3, unless the <var>COMPRESS</var> parameter appears in the <var>JANUS DEFINE</var> command for a port, no compression will be performed no matter what the JANUS WEB ON rule or $Web_Set <var>COMPRESS</var> setting specifies.

	Under <var class="product">Sirius Mods</var> Version 6.4 and later, '''no''' compression is performed unless the <var>[[NCMPBUF parameter\|NCMPBUF]]</var> system parameter is set to a non-zero value. If NCMPBUF is set to a non-zero value, the type of compression performed for a URL is determined by the [[JANUS DEFINE]] command, which can be overridden by a JANUS WEB ON rule, which can be overridden with $Web_Set.		Under <var class="product">Sirius Mods</var> Version 6.4 and later, '''no''' compression is performed unless the <var>[[NCMPBUF parameter\|NCMPBUF]]</var> system parameter is set to a non-zero value. If NCMPBUF is set to a non-zero value, the type of compression performed for a URL is determined by the <var>[[JANUS DEFINE]]</var> command, which can be overridden by a JANUS WEB ON rule, which can be overridden with $Web_Set.

	<li>If you want no compression to be the default but want to apply compression selectively for some URLs or applications, you '''must''' explicitly specify <code>COMPRESS 0</code> in the JANUS DEFINE command, and, if <var class="product">Sirius Mods</var> Version 6.4 or later, you must specify a non-zero <var>NCMPBUF</var> value for User 0.		<li>If you want no compression to be the default but want to apply compression selectively for some URLs or applications, you '''must''' explicitly specify <code>COMPRESS 0</code> in the JANUS DEFINE command, and, if <var class="product">Sirius Mods</var> Version 6.4 or later, you must specify a non-zero <var>NCMPBUF</var> value for User 0.

JAL2: /* Overview */

2012-06-22T21:02:40Z

Overview

← Older revision		Revision as of 21:02, 22 June 2012
Line 5:		Line 5:

	==Overview==		==Overview==
			Indicates the type of compression to be performed on outgoing <var class="product">[[Janus Web Server]]</var> data. Data compression reduces network bandwidth requirements for the compressed data but requires additional CPU resources to perform the compression. Janus provides deflate compression (RFC 1951), which is implemented on all modern web browsers and which works especially well for data that has frequently repeated, relatively long strings of bytes (for example, structured text data like HTML or XML).
	Indicates the type of compression to be performed on outgoing <var class="product">[[Janus Web Server]]</var> data. Data compression reduces network bandwidth requirements for the compressed data but requires additional CPU resources to perform the compression. Janus provides deflate compression (RFC 1951), which is implemented on all modern web browsers and which works especially well for data that has frequently repeated, relatively long strings of bytes (for example, structured text data like HTML or XML). <~~blockquote~~>No compression is ever performed on data with a mime-type that starts with '''image''' (for example '''image/gif''' or '''image/jpeg'''). Since most image formats are already compressed, trying to further compress them results in considerable CPU overhead and an ''increase'' in the size of the data sent (due to compression infrastructure overhead), but no real compression.</~~blockquote~~>		<p>
			'''Note:''' No compression is ever performed on data with a mime-type that starts with '''image''' (for example '''image/gif''' or '''image/jpeg'''). Since most image formats are already compressed, trying to further compress them results in considerable CPU overhead and an ''increase'' in the size of the data sent (due to compression infrastructure overhead), but no real compression.</p>

	==COMPRESS values==		==COMPRESS values==

JAL2 at 20:35, 2 March 2012

2012-03-02T20:35:40Z

← Older revision		Revision as of 20:35, 2 March 2012
Line 1:		Line 1:
	{{DISPLAYTITLE:COMPRESS}}		{{DISPLAYTITLE:COMPRESS}}
	<span class="pageSubtitle"><section begin="desc" /> COMPRESS level &~~amp;~~mdash; type of outgoing compression<section end="desc" /></span>		<span class="pageSubtitle"><section begin="desc" /> COMPRESS level — type of outgoing compression<section end="desc" /></span>

	<var>COMPRESS</var> is a parameter on <var>[[JANUS DEFINE]]</var>, which defines and sets characteristics of a Janus port.		<var>COMPRESS</var> is a parameter on <var>[[JANUS DEFINE]]</var>, which defines and sets characteristics of a Janus port.

JALWiccan: 1 revision

2012-03-02T20:19:49Z

1 revision

← Older revision	Revision as of 20:19, 2 March 2012
(No difference)

JAL2: /* Usage notes */

2012-03-02T20:19:48Z

Usage notes

JAL2: /* Usage notes */

2012-03-01T17:43:19Z

Usage notes

← Older revision		Revision as of 17:43, 1 March 2012
Line 27:		Line 27:
	<ul>		<ul>

	<li>The <var>COMPRESS</var> setting on a port can be overridden on a URL basis with a JANUS WEB ON rule and on an application basis with [[$Web_Set]]('COMPRESS'). However, under ''[[Sirius Mods]]'' Version 6.3, unless the <var>COMPRESS</var> parameter appears in the <var>JANUS DEFINE</var> command for a port, no compression will be performed no matter what the JANUS WEB ON rule or $Web_Set <var>COMPRESS</var> setting specifies.		<li>The <var>COMPRESS</var> setting on a port can be overridden on a URL basis with a JANUS WEB ON rule and on an application basis with [[$Web_Set]]('COMPRESS'). However, under ''Sirius Mods'' Version 6.3, unless the <var>COMPRESS</var> parameter appears in the <var>JANUS DEFINE</var> command for a port, no compression will be performed no matter what the JANUS WEB ON rule or $Web_Set <var>COMPRESS</var> setting specifies.

	Under ''Sirius Mods'' Version 6.4 and later, '''no''' compression is performed unless the <var>[[NCMPBUF parameter\|NCMPBUF]]</var> system parameter is set to a non-zero value. If NCMPBUF is set to a non-zero value, the type of compression performed for a URL is determined by the [[JANUS DEFINE]] command, which can be overridden by a JANUS WEB ON rule, which can be overridden with $Web_Set.		Under ''Sirius Mods'' Version 6.4 and later, '''no''' compression is performed unless the <var>[[NCMPBUF parameter\|NCMPBUF]]</var> system parameter is set to a non-zero value. If NCMPBUF is set to a non-zero value, the type of compression performed for a URL is determined by the [[JANUS DEFINE]] command, which can be overridden by a JANUS WEB ON rule, which can be overridden with $Web_Set.
Line 44:		Line 44:
	</p>		</p>

	<li>The <var>COMPRESS</var> parameter is available in ''[[Sirius Mods]]'' Version 6.3 and later.		<li>The <var>COMPRESS</var> parameter is available in ''Sirius Mods'' Version 6.3 and later.
	</ul>		</ul>

JAL2 at 17:42, 1 March 2012

2012-03-01T17:42:37Z

← Older revision		Revision as of 17:42, 1 March 2012
Line 2:		Line 2:
	<span class="pageSubtitle"><section begin="desc" /> COMPRESS level — type of outgoing compression<section end="desc" /></span>		<span class="pageSubtitle"><section begin="desc" /> COMPRESS level — type of outgoing compression<section end="desc" /></span>

	<var>COMPRESS</var> is a parameter on [[JANUS DEFINE]], which defines and sets characteristics of a Janus port.		<var>COMPRESS</var> is a parameter on <var>[[JANUS DEFINE]]</var>, which defines and sets characteristics of a Janus port.

	==Overview==		==Overview==

	Indicates the type of compression to be performed on outgoing ''[[Janus Web Server]]'' data. Data compression reduces network bandwidth requirements for the compressed data but requires additional CPU resources to perform the compression. Janus provides deflate compression (RFC 1951), which is implemented on all modern web browsers and which works especially well for data that has frequently repeated, relatively long strings of bytes (for example, structured text data like HTML or XML). <blockquote>No compression is ever performed on data with a mime-type that starts with '''image''' (for example '''image/gif''' or '''image/jpeg'''). Since most image formats are already compressed, trying to further compress them results in considerable CPU overhead and an ''increase'' in the size of the data sent (due to compression infrastructure overhead), but no real compression.</blockquote>		Indicates the type of compression to be performed on outgoing <var class="product">[[Janus Web Server]]</var> data. Data compression reduces network bandwidth requirements for the compressed data but requires additional CPU resources to perform the compression. Janus provides deflate compression (RFC 1951), which is implemented on all modern web browsers and which works especially well for data that has frequently repeated, relatively long strings of bytes (for example, structured text data like HTML or XML). <blockquote>No compression is ever performed on data with a mime-type that starts with '''image''' (for example '''image/gif''' or '''image/jpeg'''). Since most image formats are already compressed, trying to further compress them results in considerable CPU overhead and an ''increase'' in the size of the data sent (due to compression infrastructure overhead), but no real compression.</blockquote>

	==COMPRESS values==		==COMPRESS values==
Line 37:		Line 37:
	Under ''Sirius Mods'' 6.4 and later, a <var>JANUS DEFINE COMPRESS</var> setting allocates only as many extra buffers as the value of <var>NCMPBUF</var>, but these buffers are nearly five times as large as the 6.3 compression buffers.		Under ''Sirius Mods'' 6.4 and later, a <var>JANUS DEFINE COMPRESS</var> setting allocates only as many extra buffers as the value of <var>NCMPBUF</var>, but these buffers are nearly five times as large as the 6.3 compression buffers.

	<li>It is recommended that any site interested in using compression experiment with the <var>COMPRESS</var> parameter to determine compression efficiency and CPU overhead. ~~''[[~~Janus Web Server~~]]''~~ issues message MSIR.0690 after compressing any data to indicate the success of the compression.		<li>It is recommended that any site interested in using compression experiment with the <var>COMPRESS</var> parameter to determine compression efficiency and CPU overhead. <var class="product">Janus Web Server</var> issues message MSIR.0690 after compressing any data to indicate the success of the compression.
	A typical message might look like this:		A typical message might look like this: